In a small saucepan, bring water, sugar, orange zest & mint to the boil. Reduce heat immediately and simmer until sugar dissolves (It's important to make sure the sugar dissolves completely, otherwise it's a disaster).

Strain to remove the mint, then put the syrup back into the pan.

Add apples & cook until the apples are soft and pulpy. Take saucepan off heat and allow to cool (you can cheat & put this in the fridge if you like to speed the process up)

Put orange juice, lemon juice, and orange-flavored liqueur or Grand Marnier (if you're using them) into a blender along with the apple-mint syrup. Blend until smooth.

Remove from the freezer about 10 minutes before serving - this allows it to soften slightly - then either process the granita in a food processor or use a fork scrape it into fine crystals.

Alternative method - Place plastic wrap over pan and place pan in freezer. After 45 min or when ice-crystals have begun to form around edges of pan, use a fork to scrape up frozen chunks and mix into the rest of the frozen mixture. Return to freezer and continue to "rake" granita every 30 to 45 minutes until there isn't any liquid left in the granita.

To serve spoon granita into dishes or glasses and garnish with mint. Serves 4 - 6.